Helictites: Intricate Straws of Stone
Helictites are intriguing formations because they grow at all sorts of angles, seemingly defying gravity. They have a central tube that water passes through during their growth, but this tube is on a microscopic scale (0.008 to 0.5 mm in diameter). They form by seeping water and capillary action rather than by dripping water. It is unusual to see drops of water on the ends of helictites. Helictites originate at a very small hole in the side of a formation (like a column or soda straw) or in the calcite coating on a wall. The hole is small enough that water moves because of capillary action (water will rise through a small tube) or hydrostatic pressure rather than because of gravity. This explains why helictites do not grow straight down, but it does not explain why they curl and twist. This may be caused either by impurities or by the way the wedge-shaped calcite crystals stack upon each other. In some areas, particularly the West Room, there are a different variety of helictites, known as butterfly helictites.
Last updated: February 28, 2015